(R)-5-(2-aminoethyl)-1-(6,8-difluorochroman-3-yl)-1,3-dihydroimidazole-2-thione hydrochloride is described in WO2004/033447, and is useful as a medicament for treating disorders where a reduction in the hydroxylation of dopamine to noradrenaline is of therapeutic benefit. Such disorders include cardiovascular disorders, for example, hypertension and chronic heart failure.